# The Rules of the Air Regulations 1996, Paragraph 25: Flight within controlled airspace


(1) Within Class B airspace:
(a) an aircraft flying within Class B airspace at or above flight level 100 shall remain clear of cloud and in a flight visibility of at least 8 km;
(b) an aircraft flying within Class B airspace below flight level 100 shall remain clear of cloud and in a flight visibility of at least 5 km.
(2) Within Class C, Class D or Class E airspace:
(a) an aircraft flying within Class C, Class D or Class E airspace at or above flight level 100 shall remain at least 1500 metres horizontally and 1000 feet vertically away from cloud and in a flight visibility of at least 8 km;
(b) subject to sub-paragraph (c), an aircraft flying within Class C, Class D or Class E airspace below flight level 100 shall remain at least 1500 metres horizontally and 1000 feet vertically away from cloud and in a flight visibility of at least 5 km;
(c) sub-paragraph (b) shall be deemed to be complied with if:
(i) the aircraft is not a helicopter and is flying at or below 3000 feet above mean sea level at a speed which, according to its airspeed indicator, is 140 knots or less and it remains clear of cloud, in sight of the surface and in a flight visibility of at least 5 km; or
(ii) the aircraft is a helicopter flying at or below 3000 feet above mean sea level and it remains clear of cloud and in sight of the surface.

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Source: https://www.legislation.gov.uk/uksi/1996/1393/schedule/FIRST/paragraph/25 (the official version)
Page: https://openlegislation.uk/rules-of-the-air-regulations-1996/schedule-FIRST/paragraph-25
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.